I think a separation needs to be done in this discussion between texting, voice calls while holding the the phone and then true integrated hands free. Dialling is an issue separate from talking.
I would like to suggest the following:
1. texting while driving = total madness
2. dialing while driving = total madness
3. talking while holding the phone = a slight departure from reality
4. talking totally hands free = no worse than talking to a passenger
5. having young kids in the car = about halfway between 3 and (1/2)
Others have argued that a passenger is less of a distraction than a hands free call, but I believe that is probably more of an individual thing, because I use a hands free and when a call comes in and something on the road get busy, I zone out of the conversation in the same manner as when talking to a passenger, where as others may not.
One other thing I would like to add is that menu driven infotainment systems should be banned long before handsfree mobile phones, as they are almost as dangerous a distraction as texting. Of course they could be fixed by requiring the handbrake to be engaged much like the navigation menus on a GPS

A gun is (usually) intended for self defense, and its use, unless while calling the police, is not normally distracted by a cell phone conversation.
One can lose the right to drive by speeding. This is a definite threat to others. It is not necessary for an accident to result, simply driving the vehicle above the posted limit is sufficient to endanger others.
In the same way, concentration directed to a mobile communication reduces the level of safety cogitation to others who share the same roadway. And unfortunately vehicle dashboard design does not help - where at one time knobs and buttons could be sensed by touch, today's modern designs are flat with no tactile texture to the buttons. Flat screen displays are the worst offenders, they REQUIRE the removal of eyes from the road to view the screen. Not designed by monkeys, rather these are designed by morons.

True. If someone proves that he can't be responsible behind the wheel, their license to drive is revoked.
But look at it the other way around. If someone meets the age limit and has not given any indication that he would be a threat to others, does anyone have the "right" to withhold his "driving privilege"?
That's my point.
This is not much different from owning a gun. Any yahoo can buy a gun, and claim his God-given second amendment right to do so. And the next day, he can go on a shooting rampage. So in fact, this is not much different from driving.

"I rode up to her and said 'Aye, young lady,
Me donkey he will carry two.'"
"Well, seeing as ye have a donkey,
To the Dingle Fair I'll ride with you." (traditional song)
Back then donkeys did not crash into each other even when their drivers/riders were distracted or inebriated, and certainly not by cell phones. Similar to the government-regulated sharing of the RF frequency spectrum, sharing of the public roadway became a problem when the donkeys and horses were replaced by high-speed pistons. When someone does endanger others unduly they lose the privilege of driving. They can thereafter walk, or buy a donkey.

Not disagreeing with your proposals, but I do strongly disagree with this notion that driving is a "privilege," implying we should genuflect in front of the bureaucrats that "allow" us to drive.
Driving is no more a "privilege" than breathing air is, or riding a donkey was in the old days. Driving is our current form of private transportation. No one even dreamed of adding "riding a horse" as a "right" under the Constitution. Or for that matter, driving a horse-drawn cart. It was a given, that people could move about as they pleased, and carry on with their business as necessary.
So when I hear "driving is a privilege," it sounds like so much sanctimonious claptrap. We, the people, have enacted certain laws to make sure that those who drive don't endanger others unduely, but that's about the extent of the "privilege" nature of driving. We do not need to beg anyone for the "privilege" to move about.
Perhaps it's mostly a matter of semantics.

There are other reasons that the 6 digit device doesn't exist. One is that in an emergency, an otherwise normal person my be so hyped up that memorizing a 6 digit number and keying it in would be very difficult. Immobilizing a car for 60 minutes under those circumstances would be about as criminal as drunk driving.
How do you keep people from texting while driving? Ultimately, you can't. After the fact penalties are ok by me, but they don't sweep the driving population clean of scofflaws, and they don't help the family that is maimed by losing a mother or father. In the number of people driving in the US, a large number are impaired one way or another at any given time. Not much you can do except set up your penalties, and hope for the best. Similarly, banning spoons won't affect the number of obese people in the US, nor would fining people for being overweight.
These are problems in human behavior, and it will not be readily solved by gimmicks or engineering toys. Life is risky, and the amount of risk we can remove is limited.

Interesting discussion. Reminds me of the DUI/DWI discussions. In the early 1960's an engineer developed a simple device to prevent intoxicated people from driving a car. A display flashed a 6 digit number for 3 seconds. The driver than had 15 secs to enter that number and activate the vehicle. After three failed attempts, the vehicle was disabled for 60 minutes. This would have added about $15 to the cost of a new car. Why don't we have these in cars today? Because our society has determined that driving is a RIGHT, not a privlege, despite what the law actually states.
Until recently in my city, a driver could beat a DUI charge by simply refusing to blow in the tester.
I think that developing a technology to prevent cell phone (mobile phone, mate) usage may be just another way of telling abusers that if they can find a way around the tech, their behavior is acceptable. In other words, if you don't get caught, it's OK.
I agree with zeeglen that a better solution would prevent the problem, but no one will implement or use it. I like Robotics Developer's idea, even though it is 'after the fact'.
Look at the drunk driving laws in Iceland for example.
Here is my proposal:
If there is an accident and it can be determined that the operator of the vehicle was texting, then they lose the car, have a $5,000 fine, and a 30 day license suspension. Second offense, they lose the car, $10,000 fine, 1 year suspension. Third offense, they lose the car, $20,000 fine, 1 year in jail, and lifetime license suspension.
For an accident whilst talking on the phone, the punishiments would be similar, but scaled down a little.
And, if three sober citizens will testify that a driver caused an accident that killed another person and the driver was on the phone AND drunk, we just shoot them right there.

zeeglen, your observation that engineers don't believe that they can do 3 things at once with full attention is a good one. But I disagree that drivers shouldn't be held responsible for their actions. Surely, someone is responsible, and the driver looks like a good bet. On the other hand, holding the driver responsible doesn't have to be the only steps that are taken to mitigate a problem; other mechanisms can be put in place. What certainly won't work is to rely only on those mechanisms... it will not be practical to design a system that knows when it's the driver, in motion, talking or texting, but not a passenger. You can only make driving completely safe if you limit speeds to something between 0 and 5 mph. Just like spaceflight: keep the vehicle on the ground, spaceflight is safe. Except for Apollo 1.

Anyone here who has also viewed the same topic on other public forums will note a major difference in these comments - nobody here (maybe because the commenters are engineers with common sense) claims to be a superhuman multitasker who can devote 100% of their mental faculties to driving while at the same time devoting the other 100% of their mental faculties to the cell phone conversation/texting.
Right...
I cannot agree with holding drivers responsible for their actions. This happens AFTER the fact; I do not wish to become a victim of an irresponsible moron whose accountability becomes just a fine to the state. Again, the prevention needs to happen BEFORE an innocent victim becomes maimed for life. Only carrier shutdown of moving devices can accomplish this.

I love the discussion that followed the article! I can't agree with the ban, only with holding drivers responsible for their actions. I have seen many drivers (mostly women for some reason) talking on cell phones thru red lights, not signaling and turning, weaving, slowing down (10-15 mph below speed limit), and making bad driving decisions. Still, it should be punished as a moving violation like DUI. If the cellphone records show the driver on a call during the accident then: added fine and loss of license (for some period; increasing with repeats). Just a thought..